One means of exposing photographic materials is a known image forming method using a so-called scanner system. An original is scanned and a silver halide photographic material is exposed on the basis of the resulting image signal so as to form a negative image or positive image corresponding to the image of the original thereon.
There are various practical recording devices which may be used in such a scanner system image forming method. The recording light sources for scanner system recording devices include a glow lamp, a xenon lamp, a mercury lamp, a tungsten lamp and a light emitting diode. However, all these light sources have the drawbacks that the output is weak and their life is short. To compensate for these drawbacks, there are known scanners which use coherent laser rays, such as a Ne-He laser, an argon laser or a He-Cd laser, as the light source for the scanning system. The coherent laser rays may yield a high output, but they have other drawbacks in that they need large-sized, high-priced devices and modulators. In addition, since visible rays are used, the safelight for the photographic materials is limited and the handlability of the devices is poor.
In contrast, devices for semiconductor lasers are small-sized and low-priced and may be easily modulated. In addition, semiconductor lasers have a longer life than the above-mentioned lasers. Moreover, since they emit infrared rays, a light safelight may be used in handling infrared-sensitive photographic materials. Therefore, semiconductor lasers are advantageous with respect to handlability and operability. Despite these advantages, since there are unknown excellent photographic materials having high infrared sensitivity and good storage stability, the excellent characteristics of these semiconductor lasers could not be utilized satisfactorily.
In one known technology for producing photographic materials, cyanine dyes of a certain kind are added to silver halide photographic materials so as to extend their light-sensitive range on the side of a longer wavelength. This is a so-called spectral sensitizing technology. It is also known that the spectral sensitizing technology may apply not only to rays of a visible range, but also to those of an infrared range. For infrared sensitization, sensitizing dyes capable of absorbing infrared rays are used, which are described in, for example, Mees, The Theory of the Photographic Process, 3rd Ed. (published by MacMillan, 1966), pages 198 to 201. In that case, the photographic materials desirably have a high sensitivity to infrared rays and a small variation in sensitivity, even during storage of the emulsions. For this purpose, various sensitizing dyes have heretofore been developed.
For instance, many sensitizing dyes are described in U.S. Pat. Nos. 2,095,854, 2,095,856, 2,955,939, 3,482,978, 3,552,974, 3,573,921 and 3,582,344. However, even though these sensitizing dyes are used, the sensitivity and storage stability of the photographic materials to which they are added could not be said to be fully sufficient.
On the other hand, it is also known that addition of a second specifically selected organic compound of a certain kind to the photographic materials, in addition to spectral sensitizing dyes, noticeably increases the spectral sensitivity of the materials; and the effect to be attained by the addition is known as a supersensitizing effect.
For supersensitization in the infrared range, JP-A-59-191032, JP-A-59-192242 and JP-A-60-80841 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") describe the combination of infrared sensitizing dyes (tricarbocyanine dyes, 4-quinolinedicarbocyanine dyes) and cyclic onium salt compounds or heterocyclic compounds of certain kinds.
In accordance with the proposals in these patent publications, the infrared sensitivity and the storage stability of photographic materials can surely be improved. However, other techniques for obtaining even higher infrared sensitivity without lowering storage stability are desired.
On the other hand, the image quality of the images obtained by scanning exposure is not always satisfactory at least at present, and further improvement in their image quality is desired.
In addition, the speed of processing photographic materials with automatic developing machines has been elevated recently. In such rapid processing, however, the time necessary for fully decoloring the dyes in the photographic materials processed could not always be ensured so that the processed materials often have trouble due to remaining color therein.